<template>
  <div class="spec-preview">
    <img :src="imgList[defaultIndex]?.imgUrl" />
    <div class="event" @mousemove="moveMask"></div>
    <div class="big" >
      <img :src="imgList[defaultIndex]?.imgUrl" ref="big"/>
    </div>
    <div class="mask" ref="mask"></div>
  </div>
</template>

<script>

  export default {
    name: "Zoom",
    props:['imgList'],
    data() {
      return {
         defaultIndex : 0
      }
    },
    mounted(){
      this.$bus.$on('getIndex',(index)=>{
        this.defaultIndex =index
      })
    },
    methods:{
      moveMask(e){
        //鼠标的位置-蒙版的一半

        //鼠标的位置
        const mouse={
          x:e.offsetX,
          y:e.offsetY
        }
        //蒙版的大小
        const mask={
          width:this.$refs.mask.offsetWidth,
          height:this.$refs.mask.offsetHeight
        }
        //蒙版的移动位置
        const maskOffset={
          left:mouse.x-mask.width/2,
          top:mouse.y-mask.height/2
        }

        //边界值
        if(maskOffset.left<0){
          maskOffset.left=0
        }
        if(maskOffset.left>=e.target.clientWidth-mask.width){
          maskOffset.left=e.target.clientWidth-mask.width
        }
        if(maskOffset.top<0){
          maskOffset.top=0
        }
        if(maskOffset.top>=e.target.clientHeight-mask.height){
          maskOffset.top=e.target.clientHeight-mask.height
        }
        this.$refs.mask.style.left=maskOffset.left+'px'
        this.$refs.mask.style.top=maskOffset.top+'px'
        

        this.$refs.big.style.left=-maskOffset.left*2+'px'
        this.$refs.big.style.top=-maskOffset.top*2+'px'
      }
    }
  }
</script>

<style lang="less">
  .spec-preview {
    position: relative;
    width: 400px;
    height: 400px;
    border: 1px solid #ccc;

    img {
      width: 100%;
      height: 100%;
    }

    .event {
      width: 100%;
      height: 100%;
      position: absolute;
      top: 0;
      left: 0;
      z-index: 998;
    }

    .mask {
      width: 50%;
      height: 50%;
      background-color: rgba(0, 255, 0, 0.3);
      position: absolute;
      left: 0;
      top: 0;
      display: none;
    }

    .big {
      width: 100%;
      height: 100%;
      position: absolute;
      top: -1px;
      left: 100%;
      border: 1px solid #aaa;
      overflow: hidden;
      z-index: 998;
      display: none;
      background: white;

      img {
        width: 200%;
        max-width: 200%;
        height: 200%;
        position: absolute;
        left: 0;
        top: 0;
      }
    }

    .event:hover~.mask,
    .event:hover~.big {
      display: block;
    }
  }
</style>